Multiple hydraulic system



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Jan.. 16, 1934. F, w, DAVls MULTIPLE HYDRAULIC SYSTEM Filed Jan. 22,` 19:51

Patented- Jan. 16, 1,934

UNITED STATES PATENT- OFFICE l Claim.

'I'his invention relates to apparatus including a plurality of hydraulically-operated mechanisms which are connected in series in a circuit through of gears, opening of doors, etc.

which power fluid is caused to flow by a pump or other equivalent means. This application ls a continuation in part of my application Serial No. 205,634, led July 24, 1927, pursuant to which Patent No. 1,846,089 was granted February 23, 1932. As therein shown a pair of mechanisms actuable by power uid may be joined in a series containing a power pump, the mechanisms being of such a type as to permit a substantially unobstructed flow of the power fluid therethrough when not in operation. These mechanisms are also characterized by the fact that when they are in operation, power fluid is-discharged therefrom at the .same rate at which it is received through.

a supply pipe. Any suitable power iiuid, preferably an incompressible fluid, may be employed, such, for example, as an oil or glycerine mixture. For convenience and brevity the power uid is hereinafter referred to as oil, but it is to be understood that the invention is not'limited to any particular iiuid or mixture of uids.

It is the purpose of the present invention t connect together twov 4or more power actuable devices in a single fluid circuit, the arrangement being such that a predetermined maximum pressure is available for each of the several mechanisms, the pressure for each mechanism being predetermined according to its individual requirements. While the invention may be applied in any situation where it is desiredto operate by power a number of mechanisms from a single pump, as a particular illustration of the invention it is shown on the drawing as applied to an automotive vehicle,` such as an automobile,a truck, or' a bus. In passenger busses particularly, there is a great deal of physical work to be done by the operator in the ordinary operation thereof. This includes steering, application of brakes', shifting According to the present invention, these laborsmay be performed largely or wholly by power means which include a single pump supplying oil to all the operating l of mechanisms which may be employed in an automobile, together with the conventional showing of connecting piping and relief valves.

Figure 2 is an elevation, partly in section, of one 'the pump 10.

(Cl. (io-52) such mechanism, illustrating an open type of valve,

Figure 3 is a conventional showing of the elements of a combined relief and check valve suitable for use in by-passes around the several mechanisms.

Fig. 4 is a conventional showing of an ordinary spring pressed relief valve for by-passing oil from the discharge line of the last motor in series to the oil reservoir.

In Figure 1 of the drawing a pump 10 is conventionally shown, this pump being' of any desirable construction capable of delivering a substantial stream of oil at the pressure desired. The

pump discharges intol a pipe li'ne l1 which leads t@ .'to'a power steering mechanism 12. .From this steering mechanism a discharge pipe 13 may extend to a power mechanism 14 for the operation of the vehicle brakes. The pipes A11 and 13 may be connected by a by-pass 15 containing a relief valve 16 which may be of any suitable springpressed type such as are well known to the trade. Such'- a valve, as illustrated in Figure 3, may be readily adjusted so as to open when the pressure at the supply end exceeds the back pressure, at the delivery end by a definite amount which can be regulated by means of an adjustable spring. The discharge line 20 from the brake mechanism` 14 may lead to a gear shiftingi mechanism 21,

the discharge line 2 2 from this mechanism leading to another mechanism 23 which may be employed to open and close the doors of the vehicle. In like manner, other fluid motors may be added to the series for performing any service desired. As shown, a relief vbypass l5 containing a springpressed relief valve 16 may be shunted around each one of the several mechanisms employed.

The discharge line 24 from the last of the series of power actuable mechanisms may beconnected directly to the oilin'g system of the prime mover throughva reliei valve 33 and connecting pipe 29,`excess oil being allowed to escape through the valve 33 and a pipe 31 into a .suitable reservoir such as the base of the prime mover, from 'which a supply pipe 32 leads to the intake end of The power mechanism 12? ofthe steering gear `may be similar to those described and illustrated in my Patents NOS. 1,790,620 and 1,874,248. These` patents illustrate mechanism .including an substantially unobstructed stream. In some forms of ,the valve mechanism, the supply stream' may be divided into two branch streams which unite again at the discharge line. Each of these branch streams is in constant communication respectively with the chambers at the opposite ends of a power piston which may be operatively connected with the drag link of the vehicle. The valve thus permits substantially unobstructed low o' the oil through the parallel passages when the mechanism is not in operation. If the control member of the valve is moved relatively to the piston, the eect is to constrict one ofv the branch channels near the supply end and to constrict the other branch channel near the Adischarge end so that the oil is to a greater or less extent cut oi from the former channel and is diverted to the latter channel in which pressure is built up owing to the constriction near the discharge end. This pressure is instantly communicated to the corresponding pressure chamber and is exerted against the adjacent end of the piston. This tends to produce motion in the piston which results in deflection of the vehicle wheels to alter the direction of motion of the vehicle. A valve of this type is illustrated in Figure 2. As therein shown, the supply pipe 11 may lead to a longitudinal channel 40 formed in the piston 41. This piston, as shown, may be hollow to contain a valve member 42 which is slidably tted therein.' In the inner surface of the piston are cut ve annular channels 43, 44, 45, 46 and 47. In the outer surface of the valve member 42 are cut a'pair of annular grooves 50 and 51, these grooves being definitely related to the grooves in the inner surface of the piston. The grooves 43 and 47, as shown, communicate directly with a second longitudinal groove 48 in the piston so that these grooves are directly connected at all times with the discharge pipe 13. 'Ihe central groove 45 is likewise at all times connected with the supply groove 49.

The groove 44 is connected as by a seriesV of longitudinal passages 52 with a pressure chamber 53 at one end of the piston. In like manner, the groove 46 is connected by a series of longitudinal channels 54 with a pressure chamber 55 at the opposite end of the piston. If the pressures in the grooves 44 and 46 are balanced, the pressures in the chambers 53 and 55 will likewise be balanced and no resultant force will be exerted by the power fluid on the piston. If, however, the pressures in the channels 44 and 46 be changed so as to differ, this derence of pressure ls also imparted to the chambers53-and 55 so that there isla resultant pressure on one end or the other of the piston tending to move the piston. When the piston and the valve slide are in the neutral relative position shown in Figure 2, the oil fiows in through the supply pipe 11 to the groove 45. From this groove the oil iows through the grooves 50 and 51 to the discharge grooves 43 vand 47. As the arrangement of grooves is symmetrical, the pressures in the grooves 44 and 46, and hence in the chambers 53 and 55, are equal. It the Valve slide 42 is moved relatively to the piston 41, the balance of pressure is disturbed with a resulting dierenceof pressures in the chambers 53 and 55. If, for example, the slide 42 is moved to the left, as shown in Figure 2, this motion tends to reduce or cut oi entirely communication between the supply groove 45 and the connecting groove 50. Hence the supply of power uid to the groove 44, and hence to the chamber 53, is reduced. The motion of the groove 50 at the same time increases the. area of communication between the groove 44 and the dis- Leggete charge groove 43 so that discharge of liquid from the chamber 53 is facilitated. This movement ofV the slide 42 also diminishes or cuts ol communication between the discharge groove 47 and the communicating groove 51. Hence the escape of iiuid from the groove 51 is curtailed or cut oi. At the same time the motion of the groove 5l increases its communication with the supply groove 45 so that the introduction of oil to the groove 46, and hence to the chamber 55, is facilitated. The cutting o of the groove 51 from the vdischarge line tends to oppose the passage of oil past the groove 51 and hence to build up back pressure in the supply line, which pressure is communicated to the chamber 55. This building up oi pressure in the chamber 55 tends to produce a follow-up movement on the .part .of the piston to restore the piston to its normal position relative to the slide 42. Thus, by moving the slide in one direction or the other, the piston is caused by the oil. pressure to follow this motion. Hence a very slight manual steering effort can be instantly augmented with a powerful fluid pressure.

The slide 42 may be connected to the steering lpost through any desired linkage which may include a rod 60. This rod may be located within a hollow stem 61 connected to the piston, the stem 61 being passed through the end of the housing with a duid-tight packing. l

It is evident that the open type of valve illustrated in Figure 2 is characterized by open channels through which the oil may flow substantially unobstructed when the follow-up mechanism is not actively in operation. During the operation of the mechanism, oil under pressure enters one of the opposing chambers so as to move the piston. This motion of the piston displaces an equal quantity of oil from the opposite chamber, the displaced oil being discharged through the discharge pipe leading from the mechanism. equal to the rate of supply so that in the uid circuit as a whole, there is a substantially constant uninterrupted ow of oil at all times when the pump is operating, regardless of whether one or more of the fluid motors in the series is operating or not. The valve shown in Figure 2 is but one of several varieties of speciiic valve structure which may include the feature of uninterrupted ow of power fluid therethrough. Such a valve may be double-acting as shown, or may be single-acting as shown and described in my Patent No. 1,846,089, the piston being actuated in one direction by a spring or its equivalent. So far as the present invention is concerned, the particular details of structure of the valve are not material, provided only that the stream of power uid therethrough is not interrupted and, when the corresponding motor is not operating, is substantially unobstructed. Each of the motors in the circuit is preferably controlled by such an open type of valve, each of these control valves being characterized by an unobstructed ow of oil therethrough when its corresponding motor is not operating. Thus the pump normally Works against no more back pressure than that arising from the uid friction oi' the oil within the piping in the circuit and the channels and passages in the motors themselves.

Whenever a motor is operated, however, the action of the valve is to close oilE partly or wholly the pasages therethrough in order to deect the supply stream of oil into one of its pressure chambers and to facilitate the escape of oil from the The rate of discharge is obviously opposite chamber. This constriction of the passages results in a building up of more or less back pressure in the supply line. The pump must work against this back pressure in operating the motor. In case two or more motors are operated at once, each motor will operate against the back pressure produced by the motor or motors operating further along in the series. so that the pump will then work against the sum of such back pressures.

In order to insure a definite maximum available working pressure for each'of the motors in lthe series according to their several requirements,

the separate by-passes with their relief valves 16 are provided for the motors. As shown, for example, -in Figure 3, each relief valve 16 may have a spring pressed valve member 70 between a lower chamber 'Z1l and an upper chamber 72, the lower chamber communicating with the supply line to .one of the uid motors, the upper chamber communicating with the discharge line from the same motor. By adjusting a spring '73, the valvemember 70 may be regulated to lift at any predetermined excess of pressure in the chamber 'I1 over that in the chamber '12; There may also be supplied a check valve between the chambers to relieve any excess of pressure in the chamber 72 over Vthat in the chamber 71. This check valve may be in the form of a ball '14 lightly held by a spring '15 in a' suitable aperture between the chambers. 'Ihus if any motor is operated by hand -when the pump 10 is stopped, the oil which is forced along by the motion of the piston therein can circulate freely around the local by-pass and past the valve 74.

When. none of the motors in the circuit is operating, there is practically no load on thepump 10. When any of the motors is operated, a back pressure is set up-in the line, against which the pump must work. If two or more motors operate simultaneously, their back pressures are additive, that is, the pump must work against the sum of the individual back pressures. Thus, for exexample, if the steering motor 12 and the brake motor 14 operate simultaneouslmthe back press ure set up by the brake-motor acts against the low pressure side ofthe steering-motor piston, so that the pressure built up in the supply line 11 must be sufficient to move the steering-motor piston against the steering resistance and the back pressure in the line 13. Since the back pressure in the line 13 also acts against the low side of the relief valve 16 of the steering motor, this valve does not open until the difference -of pressure between the twov chambers of the steeringmotor exceeds that for which the relief valve is set. If this relief valve is set to open at 300 pounds pressure, there will thus be 300 pounds available for the steering gear, regardless of.

. out departing from the spirit and scope thereof as defined in the following claim.

I claim:

In an automotive carrier, a power system comprising a uid circuit including a plurality of iiuid operable motors and a power pump connected in series, a control valve for each motor, a by-pass around each motor and its control valve, a relief valve in each. said by-pass set to be opened by a pressure difference between the high and low pressure sides of the motor exceeding the maximu'm operating pressure of the motor, said system including a by-pass around each said motor with a chepk-valve adapted to'be opened by any excess' of pressure in the discharge end of the motor over the pressure in the supply end thereof.

FRANCIS W. DAVIS.

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